Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/0086—Conditioning, transformation of reduced iron ores
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/0033—In fluidised bed furnaces or apparatus containing a dispersion of the material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
  • Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
  • Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]

Definitions

• This invention relates to the reduction of particulate iron ore in fluidized beds. More particularly, it relates to a process for increasing the metallization of the reduced ore product from fluidized bed reduction processes.
• the ore is ground to fluidizable particle sizes ranging generally between about and about 10,000 microns, and averaging about 50 to about 200 microns in size.
• the finely ground ore is introduced into beds or stages and fluidized by upwardly flowing reducing gases at sufficiently high temperatures to reduce the oxidic ores to metallic iron.
• the ore is reduced in multiple stages by countercurrent contact with reducing gases at temperature generally ranging from about 1,000 to about l,800 F.
• the ore is preheated, or preheated and partially reduced from Fe 0 to a state of oxidation between Fe 0 and FeO.
• the preheated ore is progressively reduced first to FeO and then to mixtures of FeO and metallic Fe, and finally to a product comprising principally metallic iron.
• the reducing gases used in fluidized iron ore reduction processes may include any conventional reducing gases such as hydrogen, carbon monoxide, or mixtures of these and other gases, including inert gases such as nitrogen.
• hydrogen is converted to H 0 and carbon monoxide is converted to carbon dioxide.
• the reducing gases are generally introduced into the final reduction stage, known as the ferrous reduction stage, wherein ferrous oxides, i.e., FeO, are reduced substantially to metallic iron.
• the gases are partially oxidized in the final ferrous stage and ascend to the next higher stage and are ultimately removed from the uppermost stages of the ore reduction process.
• the spent reducing gases contain substantial amounts of unreacted hydrogen, carbon monoxide, or both, and these are generally recovered by removal of oxidized constituents.
• the recovered gases are reheated and recycled for further use in the process.
• lt is also known to introduce hydrocarbons directly into the final ferrous reduction stage of a multistage process to generate reducing gases in situ. For example, when methane, CH.,, is introduced into a bed of ferrous oxide and metallic iron at high temperatures, it reacts and forms CO and H 0, while simultaneously reducing the ferrous oxide to iron.
• the reducibility of particulate oxidic iron ores i.e., the ease with which they are reduced in a fluidized bed process, varies somewhat from ore to ore.
• certain ores such as Cerro Bolivar, from South America, can be relatively easily reduced in fluidized bed processes having the ferrous reduction stages maintained at relatively high temperatures ranging from about 1,300 to about l,600 F.
• Other ores are reduced with greater difficulty and may tend to reach a threshold level of metallization beyond which reduction progresses only with great difficulty.
• oxidic iron ore is reduced in steps to higher metallizations than can be achieved in conventional fluidized iron ore reduction processes.
• This invention contemplates reducing. the particulate ore in a staged cent metallization,
• the initial reduction of the ore in the fluidized beds is achieved at temperatures in the final ferrous reduction stage of about l,300 to l,600 F.
• Carbon is deposited on the ore, preferably in the final ferrous reduction stage, by injecting carbon-forming gases into said stage at conditions conducive to the deposition of carbon.
• the gas injection can comprise the addition of a light hydrocarbon such as methane, naphthas, natural gas, or even intermediate hydrocarbons, such as gas oils, and the like, which break down, crack, or otherwise liberate free carbon at the temperatures and conditions in the final ferrous reduction stage.
• reducing gases containing carbon monoxide may be used in the final ferrous reduction stage, and the carbon monoxide may itself liberate free carbon according to the reaction:
• the mole ratio of carbon monoxide to carbon dioxide in the reducing gas fed to the ferrous reduction zone is at least 10 and preferably ranges from about 15 to 20.
• the mole ratio of carbon monoxide to carbon dioxide in the reducing gas fed to the ferrous reduction zone is at least 10 and preferably ranges from about 15 to 20.
• At temperatures in the l,300 to l,600 F. range in the final ferrous reduction stage it is essential to maintain total system pressures of at least about 5 atmospheres and preferably about 8 to about 20 atmospheres. Under these conditions carbon deposition can be controlled to obtain a reduced iron ore product containing at least about 1 percent carbon and'preferably about 1.5 percent to 3 percent carbon, based on weight of total reduced ore product, in economically feasible holding times.
• the ore should be initially reduced to above about perand preferably about 88 percent to 92 percent metallization, before it is withdrawn from the final reduction stage.
• the term metallization means the percentage of total iron present as metallic Fe.
• a reducing gas comprising about 25% CO, 45% H 1.5% CO based on volumes, and the remainder nitrogen, is introduced into the bottom or final ferrous reduction stage at a temperature of about l,450 F.
• the exothermic reversion reaction produces sufficient heat to maintain the temperature in said final stage at about l,500 F.
• the total pressure in the final reduction stage is maintained at about 8 atmospheres. Under these conditions, about 2 wt. percent carbon is deposited on the surfaces of the reduced ore particles during a holding time in the final stage of about 30 minutes.
• the carbon coated product is withdrawn from the reactor through a nonfluidized line having a length of about 100 feet, through which the pressure drops to atmospheric, and is discharged into a receiving vessel maintained at atmospheric pressure.
• the temperature of the carbon coated particles is maintained at above about l,400 F. throughout the passage of the ore through the nonfluidized line and in the receiving vessel. Samples are taken from the receiving vessel and compared with samples of ore taken directly from the final reduction stage. A comparison shows that a portion of the carbon has gasified and increased the metallization from about 90 to about 92 percent. The total average time required for the passage of the ore through the nonfluidized withdrawal line and receiving vessel is about l minutes.
• Deposition of carbon by the reversion reaction depends upon the temperature, pressure, and partial pressures of carbon monoxide and carbon dioxide. At temperatures below about 850 F., the kinetics of the Earbon monoxide reversion reaction are so slow that carbon deposition is generally nil. At very high temperatures, i.e., above about l,600 F., the equilibrium for the reversion reaction shifts so far to the left that reversion is achieved only at very high pressures or carbon monoxide concentrations.
• the reduced ore particles can be discharged from the reactor without first being coated with carbon into an intermediate vessel maintained under carbon-depositing conditions. Increased metallizations can then be achieved by coating the particles in the intermediate vessel, transferring them to a low pressure receiving vessel wherein the carbon is necessarilyied by maintaining the temperature therein at appropriately high temperatures.
• the contents of the receiving vessel can be maintained at high temperatures, e.g., by keeping the coated particles fluidized with hot inert or reducing gases, or even by using mildly oxidizing gases to generate heat of reaction to compensate for the cooling effect of the endothermic reduction reaction.
• a process for increasing the metallization of particulate iron ore that has been reduced in a staged fluidized reduction process to a metallization of about v to about 92 percent comprising:

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Geochemistry & Mineralogy (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Dispersion Chemistry (AREA)
• Manufacture Of Iron (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Manufacture And Refinement Of Metals (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (12)

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Citations (5)

• 1968
  • 1968-10-16 US US768162A patent/US3637368A/en not_active Expired - Lifetime
• 1969
  • 1969-09-19 GB GB46332/69A patent/GB1273810A/en not_active Expired
  • 1969-10-10 NL NL6915382.A patent/NL163825C/xx not_active IP Right Cessation
  • 1969-10-15 JP JP44082470A patent/JPS4824606B1/ja active Pending
  • 1969-10-15 SE SE6914156A patent/SE380830B/xx unknown

Patent Citations (5)

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